/* The MIT License

   Copyright (C) 2011-2012 Zilong Tan (eric.zltan@gmail.com)

   Permission is hereby granted, free of charge, to any person
   obtaining a copy of this software and associated documentation
   files (the "Software"), to deal in the Software without
   restriction, including without limitation the rights to use, copy,
   modify, merge, publish, distribute, sublicense, and/or sell copies
   of the Software, and to permit persons to whom the Software is
   furnished to do so, subject to the following conditions:

   The above copyright notice and this permission notice shall be
   included in all copies or substantial portions of the Software.

   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
   MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
   BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
   ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
   CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
   SOFTWARE.
*/

#include <string.h>
#include "rand_tpl.h"
#include "hash.h"

uint64_t hash_fast64(const void *buf, size_t len, uint64_t seed)
{
	const uint64_t    m = 0x880355f21e6d1965ULL;
	const uint64_t *pos = (const uint64_t *)buf;
	const uint64_t *end = pos + (len >> 3);
	const unsigned char *pc;
	uint64_t h = len * m ^ seed;
	uint64_t v;

	while (pos != end) {
		v  = *pos++;
		v ^= v >> 23;
		v *= 0x2127599bf4325c37ULL;
		h ^= v ^ (v >> 47);
		h *= m;
	}

	pc = (const unsigned char*)pos;
	v = 0;

	switch (len & 7) {
	case 7: v ^= (uint64_t)pc[6] << 48;
	case 6: v ^= (uint64_t)pc[5] << 40;
	case 5: v ^= (uint64_t)pc[4] << 32;
	case 4: v ^= (uint64_t)pc[3] << 24;
	case 3: v ^= (uint64_t)pc[2] << 16;
	case 2: v ^= (uint64_t)pc[1] << 8;
	case 1: v ^= (uint64_t)pc[0];
		v ^= v >> 23;
		v *= 0x2127599bf4325c37ULL;
		h ^= v ^ (v >> 47);
		h *= m;
	}

	h ^= h >> 23;
	h *= 0x2127599bf4325c37ULL;
	h ^= h >> 47;

	return h;
}

/*
  -------------------------------------------------------------------------------
  mix -- mix 3 32-bit values reversibly.

  This is reversible, so any information in (a,b,c) before mix() is
  still in (a,b,c) after mix().

  If four pairs of (a,b,c) inputs are run through mix(), or through
  mix() in reverse, there are at least 32 bits of the output that
  are sometimes the same for one pair and different for another pair.
  This was tested for:
  * pairs that differed by one bit, by two bits, in any combination
  of top bits of (a,b,c), or in any combination of bottom bits of
  (a,b,c).
  * "differ" is defined as +, -, ^, or ~^.  For + and -, I transformed
  the output delta to a Gray code (a^(a>>1)) so a string of 1's (as
  is commonly produced by subtraction) look like a single 1-bit
  difference.
  * the base values were pseudorandom, all zero but one bit set, or 
  all zero plus a counter that starts at zero.

  Some k values for my "a-=c; a^=rot(c,k); c+=b;" arrangement that
  satisfy this are
  4  6  8 16 19  4
  9 15  3 18 27 15
  14  9  3  7 17  3
  Well, "9 15 3 18 27 15" didn't quite get 32 bits diffing
  for "differ" defined as + with a one-bit base and a two-bit delta.  I
  used http://burtleburtle.net/bob/hash/avalanche.html to choose 
  the operations, constants, and arrangements of the variables.

  This does not achieve avalanche.  There are input bits of (a,b,c)
  that fail to affect some output bits of (a,b,c), especially of a.  The
  most thoroughly mixed value is c, but it doesn't really even achieve
  avalanche in c.

  This allows some parallelism.  Read-after-writes are good at doubling
  the number of bits affected, so the goal of mixing pulls in the opposite
  direction as the goal of parallelism.  I did what I could.  Rotates
  seem to cost as much as shifts on every machine I could lay my hands
  on, and rotates are much kinder to the top and bottom bits, so I used
  rotates.
  -------------------------------------------------------------------------------
*/
#define mix(a,b,c)					\
	{						\
		a -= c;  a ^= rot(c, 4);  c += b;	\
		b -= a;  b ^= rot(a, 6);  a += c;	\
		c -= b;  c ^= rot(b, 8);  b += a;	\
		a -= c;  a ^= rot(c,16);  c += b;	\
		b -= a;  b ^= rot(a,19);  a += c;	\
		c -= b;  c ^= rot(b, 4);  b += a;	\
	}

/*
  -------------------------------------------------------------------------------
  final -- final mixing of 3 32-bit values (a,b,c) into c

  Pairs of (a,b,c) values differing in only a few bits will usually
  produce values of c that look totally different.  This was tested for
  * pairs that differed by one bit, by two bits, in any combination
  of top bits of (a,b,c), or in any combination of bottom bits of
  (a,b,c).
  * "differ" is defined as +, -, ^, or ~^.  For + and -, I transformed
  the output delta to a Gray code (a^(a>>1)) so a string of 1's (as
  is commonly produced by subtraction) look like a single 1-bit
  difference.
  * the base values were pseudorandom, all zero but one bit set, or 
  all zero plus a counter that starts at zero.

  These constants passed:
  14 11 25 16 4 14 24
  12 14 25 16 4 14 24
  and these came close:
  4  8 15 26 3 22 24
  10  8 15 26 3 22 24
  11  8 15 26 3 22 24
  -------------------------------------------------------------------------------
*/
#define final(a,b,c)				\
	{					\
		c ^= b; c -= rot(b,14);		\
		a ^= c; a -= rot(c,11);		\
		b ^= a; b -= rot(a,25);		\
		c ^= b; c -= rot(b,16);		\
		a ^= c; a -= rot(c,4);		\
		b ^= a; b -= rot(a,14);		\
		c ^= b; c -= rot(b,24);		\
	}

#define hashsize(n) ((uint32_t)1<<(n))
#define hashmask(n) (hashsize(n)-1)
#define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))

/*
  -------------------------------------------------------------------------------
  hash_jenkins() -- hash a variable-length key into a 32-bit value
  k       : the key (the unaligned variable-length array of bytes)
  length  : the length of the key, counting by bytes
  initval : can be any 4-byte value
  Returns a 32-bit value.  Every bit of the key affects every bit of
  the return value.  Two keys differing by one or two bits will have
  totally different hash values.

  The best hash table sizes are powers of 2.  There is no need to do
  mod a prime (mod is sooo slow!).  If you need less than 32 bits,
  use a bitmask.  For example, if you need only 10 bits, do
  h = (h & hashmask(10));
  In which case, the hash table should have hashsize(10) elements.

  If you are hashing n strings (uint8_t **)k, do it like this:
  for (i=0, h=0; i<n; ++i) h = hash_jenkins( k[i], len[i], h);

  By Bob Jenkins, 2006.  bob_jenkins@burtleburtle.net.  You may use this
  code any way you wish, private, educational, or commercial.  It's free.

  Use for hash table lookup, or anything where one collision in 2^^32 is
  acceptable.  Do NOT use for cryptographic purposes.
  -------------------------------------------------------------------------------
*/

uint32_t hash_jenkins(const void *key, size_t length, uint32_t initval)
{
	uint32_t a,b,c;                                          /* internal state */
	union { const void *ptr; size_t i; } u;     /* needed for Mac Powerbook G4 */

	/* Set up the internal state */
	a = b = c = 0xdeadbeef + ((uint32_t)length) + initval;

	u.ptr = key;
	if ((u.i & 0x3) == 0) {
		const uint32_t *k = (const uint32_t *)key;         /* read 32-bit chunks */
		/* const uint8_t  *k8; */

		/*------ all but last block: aligned reads and affect 32 bits of (a,b,c) */
		while (length > 12)
		{
			a += k[0];
			b += k[1];
			c += k[2];
			mix(a,b,c);
			length -= 12;
			k += 3;
		}

		/*----------------------------- handle the last (probably partial) block */
		/* 
		 * "k[2]&0xffffff" actually reads beyond the end of the string, but
		 * then masks off the part it's not allowed to read.  Because the
		 * string is aligned, the masked-off tail is in the same word as the
		 * rest of the string.  Every machine with memory protection I've seen
		 * does it on word boundaries, so is OK with this.  But VALGRIND will
		 * still catch it and complain.  The masking trick does make the hash
		 * noticably faster for short strings (like English words).
		 */
#ifndef VALGRIND

		switch(length)
		{
		case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
		case 11: c+=k[2]&0xffffff; b+=k[1]; a+=k[0]; break;
		case 10: c+=k[2]&0xffff; b+=k[1]; a+=k[0]; break;
		case 9 : c+=k[2]&0xff; b+=k[1]; a+=k[0]; break;
		case 8 : b+=k[1]; a+=k[0]; break;
		case 7 : b+=k[1]&0xffffff; a+=k[0]; break;
		case 6 : b+=k[1]&0xffff; a+=k[0]; break;
		case 5 : b+=k[1]&0xff; a+=k[0]; break;
		case 4 : a+=k[0]; break;
		case 3 : a+=k[0]&0xffffff; break;
		case 2 : a+=k[0]&0xffff; break;
		case 1 : a+=k[0]&0xff; break;
		case 0 : return c;              /* zero length strings require no mixing */
		}

#else /* make valgrind happy */

		k8 = (const uint8_t *)k;
		switch(length)
		{
		case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
		case 11: c+=((uint32_t)k8[10])<<16;  /* fall through */
		case 10: c+=((uint32_t)k8[9])<<8;    /* fall through */
		case 9 : c+=k8[8];                   /* fall through */
		case 8 : b+=k[1]; a+=k[0]; break;
		case 7 : b+=((uint32_t)k8[6])<<16;   /* fall through */
		case 6 : b+=((uint32_t)k8[5])<<8;    /* fall through */
		case 5 : b+=k8[4];                   /* fall through */
		case 4 : a+=k[0]; break;
		case 3 : a+=((uint32_t)k8[2])<<16;   /* fall through */
		case 2 : a+=((uint32_t)k8[1])<<8;    /* fall through */
		case 1 : a+=k8[0]; break;
		case 0 : return c;
		}

#endif /* !valgrind */

	} else if ((u.i & 0x1) == 0) {
		const uint16_t *k = (const uint16_t *)key;         /* read 16-bit chunks */
		const uint8_t  *k8;

		/*--------------- all but last block: aligned reads and different mixing */
		while (length > 12)
		{
			a += k[0] + (((uint32_t)k[1])<<16);
			b += k[2] + (((uint32_t)k[3])<<16);
			c += k[4] + (((uint32_t)k[5])<<16);
			mix(a,b,c);
			length -= 12;
			k += 6;
		}

		/*----------------------------- handle the last (probably partial) block */
		k8 = (const uint8_t *)k;
		switch(length)
		{
		case 12: c+=k[4]+(((uint32_t)k[5])<<16);
			b+=k[2]+(((uint32_t)k[3])<<16);
			a+=k[0]+(((uint32_t)k[1])<<16);
			break;
		case 11: c+=((uint32_t)k8[10])<<16;     /* fall through */
		case 10: c+=k[4];
			b+=k[2]+(((uint32_t)k[3])<<16);
			a+=k[0]+(((uint32_t)k[1])<<16);
			break;
		case 9 : c+=k8[8];                      /* fall through */
		case 8 : b+=k[2]+(((uint32_t)k[3])<<16);
			a+=k[0]+(((uint32_t)k[1])<<16);
			break;
		case 7 : b+=((uint32_t)k8[6])<<16;      /* fall through */
		case 6 : b+=k[2];
			a+=k[0]+(((uint32_t)k[1])<<16);
			break;
		case 5 : b+=k8[4];                      /* fall through */
		case 4 : a+=k[0]+(((uint32_t)k[1])<<16);
			break;
		case 3 : a+=((uint32_t)k8[2])<<16;      /* fall through */
		case 2 : a+=k[0];
			break;
		case 1 : a+=k8[0];
			break;
		case 0 : return c;                     /* zero length requires no mixing */
		}

	} else {                        /* need to read the key one byte at a time */
		const uint8_t *k = (const uint8_t *)key;

		/*--------------- all but the last block: affect some 32 bits of (a,b,c) */
		while (length > 12)
		{
			a += k[0];
			a += ((uint32_t)k[1])<<8;
			a += ((uint32_t)k[2])<<16;
			a += ((uint32_t)k[3])<<24;
			b += k[4];
			b += ((uint32_t)k[5])<<8;
			b += ((uint32_t)k[6])<<16;
			b += ((uint32_t)k[7])<<24;
			c += k[8];
			c += ((uint32_t)k[9])<<8;
			c += ((uint32_t)k[10])<<16;
			c += ((uint32_t)k[11])<<24;
			mix(a,b,c);
			length -= 12;
			k += 12;
		}

		/*-------------------------------- last block: affect all 32 bits of (c) */
		switch(length)                   /* all the case statements fall through */
		{
		case 12: c+=((uint32_t)k[11])<<24;
		case 11: c+=((uint32_t)k[10])<<16;
		case 10: c+=((uint32_t)k[9])<<8;
		case 9 : c+=k[8];
		case 8 : b+=((uint32_t)k[7])<<24;
		case 7 : b+=((uint32_t)k[6])<<16;
		case 6 : b+=((uint32_t)k[5])<<8;
		case 5 : b+=k[4];
		case 4 : a+=((uint32_t)k[3])<<24;
		case 3 : a+=((uint32_t)k[2])<<16;
		case 2 : a+=((uint32_t)k[1])<<8;
		case 1 : a+=k[0];
			break;
		case 0 : return c;
		}
	}

	final(a,b,c);
	return c;
}


/*
 * hash_jenkins2 - return 2 32-bit hash values
 *
 * This is identical to hash_jenkins(), except it returns two 32-bit hash
 * values instead of just one.  This is good enough for hash table
 * lookup with 2^^64 buckets, or if you want a second hash if you're not
 * happy with the first, or if you want a probably-unique 64-bit ID for
 * the key.  *pc is better mixed than *pb, so use *pc first.  If you want
 * a 64-bit value do something like "*pc + (((uint64_t)*pb)<<32)".
 */
void hash_jenkins2(const void *key, size_t length, uint32_t *pc, uint32_t *pb)
{
	uint32_t a,b,c;                                          /* internal state */
	union { const void *ptr; size_t i; } u;     /* needed for Mac Powerbook G4 */

	/* Set up the internal state */
	a = b = c = 0xdeadbeef + ((uint32_t)length) + *pc;
	c += *pb;

	u.ptr = key;
	if ((u.i & 0x3) == 0) {
		const uint32_t *k = (const uint32_t *)key;         /* read 32-bit chunks */
		/* const uint8_t  *k8; */

		/*------ all but last block: aligned reads and affect 32 bits of (a,b,c) */
		while (length > 12)
		{
			a += k[0];
			b += k[1];
			c += k[2];
			mix(a,b,c);
			length -= 12;
			k += 3;
		}

		/*----------------------------- handle the last (probably partial) block */
		/* 
		 * "k[2]&0xffffff" actually reads beyond the end of the string, but
		 * then masks off the part it's not allowed to read.  Because the
		 * string is aligned, the masked-off tail is in the same word as the
		 * rest of the string.  Every machine with memory protection I've seen
		 * does it on word boundaries, so is OK with this.  But VALGRIND will
		 * still catch it and complain.  The masking trick does make the hash
		 * noticably faster for short strings (like English words).
		 */
#ifndef VALGRIND

		switch(length)
		{
		case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
		case 11: c+=k[2]&0xffffff; b+=k[1]; a+=k[0]; break;
		case 10: c+=k[2]&0xffff; b+=k[1]; a+=k[0]; break;
		case 9 : c+=k[2]&0xff; b+=k[1]; a+=k[0]; break;
		case 8 : b+=k[1]; a+=k[0]; break;
		case 7 : b+=k[1]&0xffffff; a+=k[0]; break;
		case 6 : b+=k[1]&0xffff; a+=k[0]; break;
		case 5 : b+=k[1]&0xff; a+=k[0]; break;
		case 4 : a+=k[0]; break;
		case 3 : a+=k[0]&0xffffff; break;
		case 2 : a+=k[0]&0xffff; break;
		case 1 : a+=k[0]&0xff; break;
		case 0 : *pc=c; *pb=b; return;  /* zero length strings require no mixing */
		}

#else /* make valgrind happy */

		k8 = (const uint8_t *)k;
		switch(length)
		{
		case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
		case 11: c+=((uint32_t)k8[10])<<16;  /* fall through */
		case 10: c+=((uint32_t)k8[9])<<8;    /* fall through */
		case 9 : c+=k8[8];                   /* fall through */
		case 8 : b+=k[1]; a+=k[0]; break;
		case 7 : b+=((uint32_t)k8[6])<<16;   /* fall through */
		case 6 : b+=((uint32_t)k8[5])<<8;    /* fall through */
		case 5 : b+=k8[4];                   /* fall through */
		case 4 : a+=k[0]; break;
		case 3 : a+=((uint32_t)k8[2])<<16;   /* fall through */
		case 2 : a+=((uint32_t)k8[1])<<8;    /* fall through */
		case 1 : a+=k8[0]; break;
		case 0 : *pc=c; *pb=b; return;  /* zero length strings require no mixing */
		}

#endif /* !valgrind */

	} else if ((u.i & 0x1) == 0) {
		const uint16_t *k = (const uint16_t *)key;         /* read 16-bit chunks */
		const uint8_t  *k8;

		/*--------------- all but last block: aligned reads and different mixing */
		while (length > 12)
		{
			a += k[0] + (((uint32_t)k[1])<<16);
			b += k[2] + (((uint32_t)k[3])<<16);
			c += k[4] + (((uint32_t)k[5])<<16);
			mix(a,b,c);
			length -= 12;
			k += 6;
		}

		/*----------------------------- handle the last (probably partial) block */
		k8 = (const uint8_t *)k;
		switch(length)
		{
		case 12: c+=k[4]+(((uint32_t)k[5])<<16);
			b+=k[2]+(((uint32_t)k[3])<<16);
			a+=k[0]+(((uint32_t)k[1])<<16);
			break;
		case 11: c+=((uint32_t)k8[10])<<16;     /* fall through */
		case 10: c+=k[4];
			b+=k[2]+(((uint32_t)k[3])<<16);
			a+=k[0]+(((uint32_t)k[1])<<16);
			break;
		case 9 : c+=k8[8];                      /* fall through */
		case 8 : b+=k[2]+(((uint32_t)k[3])<<16);
			a+=k[0]+(((uint32_t)k[1])<<16);
			break;
		case 7 : b+=((uint32_t)k8[6])<<16;      /* fall through */
		case 6 : b+=k[2];
			a+=k[0]+(((uint32_t)k[1])<<16);
			break;
		case 5 : b+=k8[4];                      /* fall through */
		case 4 : a+=k[0]+(((uint32_t)k[1])<<16);
			break;
		case 3 : a+=((uint32_t)k8[2])<<16;      /* fall through */
		case 2 : a+=k[0];
			break;
		case 1 : a+=k8[0];
			break;
		case 0 : *pc=c; *pb=b; return;  /* zero length strings require no mixing */
		}

	} else {                        /* need to read the key one byte at a time */
		const uint8_t *k = (const uint8_t *)key;

		/*--------------- all but the last block: affect some 32 bits of (a,b,c) */
		while (length > 12)
		{
			a += k[0];
			a += ((uint32_t)k[1])<<8;
			a += ((uint32_t)k[2])<<16;
			a += ((uint32_t)k[3])<<24;
			b += k[4];
			b += ((uint32_t)k[5])<<8;
			b += ((uint32_t)k[6])<<16;
			b += ((uint32_t)k[7])<<24;
			c += k[8];
			c += ((uint32_t)k[9])<<8;
			c += ((uint32_t)k[10])<<16;
			c += ((uint32_t)k[11])<<24;
			mix(a,b,c);
			length -= 12;
			k += 12;
		}

		/*-------------------------------- last block: affect all 32 bits of (c) */
		switch(length)                   /* all the case statements fall through */
		{
		case 12: c+=((uint32_t)k[11])<<24;
		case 11: c+=((uint32_t)k[10])<<16;
		case 10: c+=((uint32_t)k[9])<<8;
		case 9 : c+=k[8];
		case 8 : b+=((uint32_t)k[7])<<24;
		case 7 : b+=((uint32_t)k[6])<<16;
		case 6 : b+=((uint32_t)k[5])<<8;
		case 5 : b+=k[4];
		case 4 : a+=((uint32_t)k[3])<<24;
		case 3 : a+=((uint32_t)k[2])<<16;
		case 2 : a+=((uint32_t)k[1])<<8;
		case 1 : a+=k[0];
			break;
		case 0 : *pc=c; *pb=b; return;  /* zero length strings require no mixing */
		}
	}

	final(a,b,c);
	*pc=c; *pb=b;
}
